Automatic prediction, selection and analysis of occultations to characterize asteroid family members

A new 50 cm telescope, the UniversCity telescope, was recently installed at Plateau de Calern, France, to survey stellar occultation by asteroids from collisional families. A stellar occultation occurs when an asteroid passes in front of a distant star blocking its light temporarily. Measuring the time of the occultations provides an accurate astrometric measurement of the asteroid, comparable with the angular size of the asteroid. Thanks to the astrometric catalog from the Gaia mission, astrometry accuracy from occultation reaches a few milliarcseconds.

The astrometry from the survey is used in turn to improve the orbit of the asteroid, while the duration of the occultation is used to constrain physical characteristics and search for binarity. The orbit improvement aims to detect and measure the drift rate in the orbital elements of asteroids due to the Yarkovsky effect, a non-gravitational force responsible for scattering the orbital elements of collisional family members. Combining the magnitude of the Yarkovsky drift rate from the occultation survey with the accumulated drift since the originating collision, the age determination of the collisional family can be obtained.

The occultation survey takes advantage of the stellar occultation technique and the Gaia astrometric catalog to systematically derive accurate astrometric measurements for collisional family members.

The telescope will be operated robotically, dedicating most of its time to the occultation survey, with a small percentage of time to other science cases. The large number of family members and candidates to stellar occultations demands the automation of the occultation prediction, the selection and prioritization of occultation events, telescope scheduling, data reduction, and data analysis.

The occultation predictions are updated regularly in the light of new astrometric measurements from traditional astrometry and from occultations measurements. The occultations predicted to be visible from the UniversCity site are prioritized based on their chances of detection and contribution to the family age determination. The data acquired each night is automatically reduced to obtain light curves from which detection candidates are analyzed.

We will present the status of the project and the development and performances of the automatic prediction and processing system.